The reasons cover songs exist today is because of an awful decision by the US Supreme Court more than a hundred years ago. And it involves player pianos, of all things. Slate reports:
Way before Spotify, stereos, or even radio, Americans who wanted to listen to music at home had one choice: They could play it themselves. This changed by the 1890s, when a hot new technology arrived: the player piano. Player pianos were miraculous in their ability to play popular songs and old standards alike while people sang along, danced, or just enjoyed the sounds. But as with a lot of newfangled machines, not everyone loved the player piano.In particular, the technology deeply troubled composers, such as the famed John Philip Sousa. Sousa worried that the pianos would kill the public’s demand for sheet music, and copyright royalties from the sale of sheet music were what paid composers’ bills. To make matters worse, the player piano companies refused to pay royalties for the songs they put on piano rolls—scrolls of paper with holes punched out in patterns. People couldn’t read the rolls; they spoke only to machines. And on that ground, the player piano companies argued that the rolls did not “copy” songs, and so could be manufactured and distributed without the need to pay royalties.
This was an exceptionally stupid argument. Sheet music and player piano rolls both copy songs; they just use different languages. What matters is what comes out when the language is translated. And for both, the answer is the same: music.